Speaking engagements have become commonplace in fields of business, entertainment, and others. The moderator at a presentation or conference must often communicate with presenters. It is most common that a moderator must inform the presenter that the allotted time has expired, but there are numerous other reasons why the moderator, director, or other organizer of a performance or presentation may wish to signal someone on the stage, platform, or otherwise before an audience.
A beeper or buzzer connected to a switch or a timer has often been used to signal a presenter that the allotted time has expired. Small headphones or earplugs capable of receiving radio transmissions were fitted to commentators so that last minute information and instructions might be given during the show. In situations where less obtrusive signaling was desired, a small light device was attached to a podium so that a moderator at a speaking engagement could send a signal to the presenter. Sometimes the moderators even made hand gestures like pointing to the wrist or a clock on the wall. In other situations, the moderator simply vocalized to the presenter the information required, tapped the speaker or performer on the shoulder, or used even a most comical and intrusive technique: a long cane with a crooked end popped out from somewhere behind the curtain, hooked around the neck of a performer and dragged him off the stage.
With the increasing popularity of multimedia presentations at business meetings and conferences, presenters often wish to be free to move about during their presentation. They may wish to mingle amongst the audience or step over to a screen or chart they are displaying. Podium lights or other visual signals are becoming less and less effective means of signaling during presentations.